Composition for use as antioxidant for motor fuels



undesirable tendency to deteriorate.

Patented Nov. 15, 1949 UNITED STATES PATENT OFFICE COMPOSITION FOR USE AS ANTIOXIDANT FOR MOTOR FUELS Harold Von Bramer, Kingsport, Tenn., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application October 8, 1946, .7 V Serial.No. 702,08]. H

Claims. (CL 252-403) on the other hand, do not ordinarily have the same undesirable tendency to deteriorate, although blended stocks containing cracked gasoline and straight-run gasoline usually show the Similar fractions of hydrocarbon distillates produced by distillation of hydrocarbonaceous materials other than petroleum and certain other hydrocarbon products, useful as motor fuels, produced by polymerization of unsaturated hydrocarbons, such as butenes and pentenes, frequently show the tendency to deteriorate upon storage.

It has been found that such deterioration of hydrocarbon motor fuels can be inhibited or retarded very effectively by incorporating therein N,N'-diisopropyl-p-phenylenediamine. Although this derivative of p-phenylenediamine has a high degree of inhibitor potency, its ordinary physical state renders it impractical for use as an antioxidant (inhibitor) as a pure substance. This derivative of p-phenylenediamine is a white solid at ordinary temperatures and does not dissolve rapidly in hydrocarbon motor fuels. Accordingly,

. it is difficult to obtain uniform distribution of the inhibitor in the motor fuels without resort to time-consuming methods of vigorous agitation of the motor fuel stock being treated. Furthermore, where huge quantities of gasolines are being stabilized with such an inhibitor on a commercial scale, methods involving vigorous agitation are wholly impractical.

It is essential in large-scale operations to be able to blend the inhibitor into the motor fuels in a manner which permits a rapid, uniform distribution of the inhibitor throughout the motor fuel. Any uneven distribution of the inhibitor throughout the treated stock is clearly undesirable.

From the practical standpoint of handling motor fuels during the treatment thereof with inhibitors, it is usually most desirable to feed the inhibitors continuously or intermittently into a flow of the fuel. However, most solid inhibitors do not ordinarily dissolve rapidly and distribute themselves uniformly throughout the motor fuel when incorporated in this manner. For this reason, it has been proposed to employ mobile solutions of solid inhibitors which can be fed into the flow of gasoline.

It is an object of this invention to provide compositions comprising N,Ndiisopropyl-p-phenylenediamine which are useful as antioxidants for, or inhibitors of the deterioration of, motor fuels. Other objects will become apparent hereinafter.

I have found that a mixture of N,N'-diisopropylp-phenylenediamine with at least one ketone selected from the group consisting of acetone, methyl ethyl ketone, diethyl ketone and methyl isopropyl ketone, said ketone constituting from about 25 to about '75 per cent by weight of the mixture, is an excellent antioxidant or inhibitor for use in hydrocarbon motor fuels. These mixtures or solutions have high color stability and stock solutions of the mixtures in gasoline retain their homogeneity at low temperatures.

Contrasted with these ketones, low molecular weight alcohols, such as methyl alcohol, ethyl alcohol, isopropyl alcohol and n-butyl alcohol, while having high solvent power for N,N- diisopropyl-p-phenylenediamine and having no seriously deleterious effect on the inhibiting potency of this phenylenediamine derivative, give solutions which are prone to discolor very rapidly. Aliphatic and aromatic hydrocarbons are excellent solvents for N,N-diisopropyl-p-phenylenediamine as far as color stability is concerned, but lose their solvent power too rapidly with decreasing temperature to be practical.

It is common practice at gasoline refineries to prepare a 20 per cent solution of an inhibitor in straight-run gasoline. Blending of this 20 per cent solution with motor fuels permits easier control of the final concentration of the inhibitor in the inhibited motor fuel. Since the tank in which the 20 per cent stock solution is prepared is normally out-of-doors, it is necessary that the inhibitor should not separate from the stock solution at temperatures normally encountered in refinery practice.

My new compositions give 20 per cent stock solutions in gasoline from which the phenylenediamine derivative separates only at low temperatures. In contrast, solutions of N, N-diisopropy1- p-phenylenediamine in benzene, Xylenes and straight-run gasoline give 20 per cent stock. solutions in gasoline from which the phenyleneration temperatures of my new compositions in V contrast to benzene, xylene and straight-run gasoline compositions.

[% Separation temperature, 0.1

75% by weight 50%by weight Solvent weight acetone methyl ethyl ketone diethyl ketone methyl isopropyl keton benzene xylenes (mixed) straight-rim gasoline From the foregoing table, the marked superiority of my new compositions over those involving benzene, xylenes and straight-run gasoline is apparent. While some alcohols give good 20 per cent separation temperatures, the color indu ed by the alcohols removes them from practical utility. Contrasted with my new compositions, solutions of N ,N '-diisopropylp-phenylenediamine in methyl n-propyl ketone or methyl isobutyl ketone containing 50 per cent by weight of the from about 40 to about 60 per cent by weight of the mixture.

My invention is directed to the stabilization of hydrocarbon motor fuels against deterioration. By the term hydrocarbon motor fuel, I mean not only motor fuels constituted entirely of hydro.- carbons, but also motor fuels containing hydrocarbons and appreciable amounts of othercombustible substances, such as alcohols or ethers.

To stabilize motor fuels against deterioration with my new composition, I dissolve a small amount of the composition in the motor fuel. Ordinarily an amount suflicient to give a concentration of from about 0.0001% to about 0.1%. (by weight) of the composition in the motor fuel will suflice to give a motor fuel of suitable stability against deterioration. Of course, the quantity of any one of m new compositions which is. actually employed will depend upon the nature of the motor fuel being stabilized and the conditions under which the fuel is stored. The tendency of the motor fuel to form gum can be determined among other methods by an accelerated oxidation test. The test described by Eglofi et a.l.,' Ind. Eng. Chem, 24, 1375 (1932) is very satisfactory and is widely used. In accordance with this test, a sample of the motor fuel being tested, in an Open 8-ounce bottle, is placed in a suitable metal bomb surrounded by a Water bath. Oxygen isintroduced to 100 pounds per square inch (7 kg, per square centimeter pressure). The bath is then heated to 100 C. As the temperature increases,

the pressure rises, reaches a maximum and continues near this maximum for a shorter or longer period of time. The test is continued for 4 hours or until a drop in pressure is noted. The period from slightly before the attainment of maximum pressure (approximately 15 minutes from the beginning of heating), until more than a slight drop in pressure takes place (usually a sharp break in the pressure occurs), is recorded as the induction period. 7

An' induction period of less than '75 minutes is usually indicative of very low stability, while an induction period of 300 or more minutes, for

freshly made motor fuels, represents a fuel possessing suitable stability for from 6 to 12 months storage in the northern half of the United States. For more southern or warmer climates, the induction period should be increased somewhat for satisfactory bulk storage of about one year duration.

My new composition can be employed to retard gum formation in hydrocarbon motor fuels which tend to undergo deterioration whether the motor fuel contains small or large amounts of addition agents, such as tetraalkyl lead compositions. It is, of course, known that tetraalkyl lead compounds, such as tetraethyl lead, are added to hydrocarbon motor fuels to improve the octane rating of the motor fuels. In some cases only a relatively small amount of the tetraalkyl lead compound is added, but sometimes with certain aviation grades of gasoline, a larger amount is used, such as with aviation gasoline having an octane number above and comprising essentially non-gum-forming hydrocarbons containing less than 1% by volume 'of Olefinic or diolefinic hydrocarbons. Motor fuels having a relatively large amount of tetraalkyl'leadcompounds are usually referred to as heavily leaded" gasoline.

Not only can my new compositions be used in all types of leaded gasoline, but mynew compositions can, if desired, be added to the ethyl fluid itself. Ethyl fluid usually is a solution containing a mixture of tetraalkyl lead compound and a halogenated hydrocarbon, such as ethylene dibromide or ethylene dichloride, or

both. My new compositionsserve to retard the formation of haze in ethyl fluid or in hydrocarbon motor fuels containing the ethyl fluid, whether the hydrocarbon motor fuel is one which forms gum upon storage or is one which is composed essentially ofnon-gum-forming hydrocarbons.

What I claim as my invention and desire to be secured by Letters Patent of the United States 1. A composition useful as an antioxidant for motor fuels consisting of- N,N--diisopropy1-pphenylenedia-mine and at least one ketone selected fromthe group consisting of acetone, methyl ethyl ketone, diethyl ketone and methyl isopropyl ketone, said ketone constituting from about 25 to about 75 per cent by weight of the mixture.

2'. A composition useful as an antioxidant for motorfuels consisting of N,N-diisopropyl-pphenylenediamine and acetone, the acetone constituting from about 25 to about 75 per cent by weight of the mixture.

3. A composition useful as an antioxidant: for motor fuels consisting of N,N-diisopropyl-pphenylenediamine and methyl ethyl ketone, the methyl ethyl ketone constituting from about 25 to about 75 per cent by weight of the mixture.

4. A composition useful as an antioxidant for motor fuels consisting of N,N-diisopropy1-pphenylenediamine and methyl isopropyl ketone, the methylisopropyl ketone constituting from about 25 to about 75 per cent by weight of the mixture.

5. A composition useful as an antioxidant for motor fuels consisting of N,N'-diisopropy1-pphenylenediamine and acetone, the acetone constituting from about 40 to about 60 per cent by weight of the mixture.

6. A composition useful as an antioxidant for motor fuels consisting of N,N'-diisopropy1-pphenylenediamine and methyl ethyl ketone, the methyl ethyl ketone constituting from about 40 to about 60 per cent by weight of the mixture.

7. A composition useful as an antioxidant for motor fuels consisting of N,N-diisopropyl-pphenylenediamine and. methyl isopropyl ketone, the methylisopropyl ketone constituting from about 40 to about 60 per cent by weight of the mixture.

8. A composition useful as an antioxidant for motor fuels consisting of N,N'-diisopropy1-pphenylenediamine and. acetone, the acetone constituting about 50 per cent by weight of the mixture.

9. A composition useful as an antioxidant for motor fuels consisting of N,N'-diisopr0py1-pphenylenediamine and methyl ethyl ketone, the methyl ethyl ketone constituting about per cent by weight of the mixture.

10. A composition useful as an antioxidant for motor fuels consisting of N,N'-diisopropyl-pphenylenediamine and. methyl isopropyl ketone, the methyl isopropyl ketone constituting about 50 per cent by weight of the mixture.

HAROLD VON BRAMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

